Dialkyne compounds

ABSTRACT

Described are dialkyne compounds of the formula I  
                 
 
     in which n, m, R 1 , R 2 , X 1 , X 2 , X 3 , X 4 , Z 1 , Z 2 , A 1 , A 2 , Q, Y 1  and Y 2  are as defined in claim  1  and the use of such compounds in liquid-crystal media.

[0001] The invention relates to dialkyne compounds of the formula I

[0002] in which

[0003] R¹ and R², independently of one another, are H, F, or an alkylradical having 1-15 carbon atoms which is unsubstituted or at leastmonosubstituted by halogen or CN and in which, in addition, one or moreCH₂ groups may each, independently of one another, be replaced by —O—,—S—, —CO—,

[0004] —CO—O—, —O—CO—, —O—CO—O— or —CH═CH— in such a way thatheteroatoms are not connected directly,

[0005] X¹, X², X³ and X⁴ are each, independently of one another, H or—C≡C—C≡C—R³, where at least one of the groups X¹, X², X³ and X⁴ is—C≡C—C≡C—R³,

[0006] R³ is H, Cl, CN, SF₅, CF₃, or an alkyl radical having 1-15 carbonatoms which is unsubstituted or at least monosubstituted by halogen andin which, in addition, one or more CH₂ groups may be replaced, in eachcase independently of one another, by —CH═CH— or —O— in such a way that—O— atoms are not connected directly,

[0007] Q is —CH₂— or —O—, and

[0008] Y¹ and Y², independently of one another, are C or Si,

[0009] A¹ and A², independently of one another, are atrans-1,4-cyclohexylene radical which is unsubstituted or substituted byF or CN and in which, in addition, one or more non-adjacent CH₂ groupsmay be replaced by —O— and/or —S—, or are

[0010] Z¹ and Z² are each, independently of one another, —CO—O—, —O—CO—,—CH₂O—, —O—, —OCH₂—, —CF₂O—, —OCF₂—, —CF₂CF₂—, —CF═CF—, —CH₂CH₂—,—CH═CH— or a single bond, and

[0011] n and m, independently of one another, are 0, 1, 2 or 3, where

[0012] m+n is 1, 2 or 3.

[0013] The invention also relates to the use of the compounds of theformula I as components of liquid-crystalline media, and toliquid-crystal and electro-optical display elements which contain theliquid-crystalline media according to the invention.

[0014] The compounds of the formula I frequently have a low positive ornegative value of the dielectric anisotropy and can be used ascomponents of liquid-crystalline media, in particular for displays basedon the principle of the twisted cell, the guest-host effect, the effectof deformation of aligned phases DAP or ECB (electrically controlledbirefringence) or the effect of dynamic scattering.

[0015] The substances employed hitherto for this purpose all havecertain disadvantages, for example inadequate stability to the action ofheat, light or electric fields, or unfavorable elastic and/or dielectricproperties.

[0016] The invention has an object of finding novel stableliquid-crystalline or mesogenic compounds having particularly lowoptical anisotropy (Δn) and negative or positive dielectric anisotropy(Δε) which are suitable as components of liquid-crystalline media, inparticular for TFT and STN displays.

[0017] Upon further study of the specification and appended claims,further objects and advantages of this invention will become apparent tothose skilled in the art.

[0018] It has now been found that the compounds of the formula I areeminently suitable as components of liquid-crystalline media. With theiraid, it is possible to obtain stable liquid-crystalline media, inparticular suitable for TFT or STN displays. The novel compounds aredistinguished, in particular, by high thermal stability, which isadvantageous for a high holding ratio, and exhibit favorable clearingpoint values. At a reduced temperature of 0.9 and a wavelength of 589nm, the compounds of the formula I have an optical anisotropy value Δnof <0.03, preferably <0.02, which is attributable to a particularlylarge value of n₁. The reduced temperature here is defined as follows:$\frac{{measurement}\quad {temperature}\quad {in}\quad K}{{clearing}\quad {point}\quad {temperature}\quad {in}\quad K} = {{reduced}\quad {temperature}}$

[0019] Liquid-crystalline media having very low optical anisotropyvalues are of particular importance for reflective and transflectiveapplications, i.e. applications in which the respective LCD experiencesno or only supporting background illumination. Low values of An areachieved by the use of substituents X¹, X², X³ and/or X⁴ having thehighest possible polarizability. Owing to the small volume of the groupsX¹, X², X³ and X⁴, the other LC properties, such as clearing point andviscosity, of liquid-crystalline mixtures to which the compoundsaccording to the invention have been added are only impaired to arelatively small extent.

[0020] Very generally, the provision of compounds of the formula Iconsiderably broadens the range of liquid-crystalline substances whichare suitable, from various applicational points of view, for thepreparation of liquid-crystalline mixtures.

[0021] The compounds of the formula I have a broad range ofapplications. Depending on the choice of substituents, these compoundscan serve as base materials of which liquid-crystalline media arepredominantly composed; however, it is also possible to add compounds ofthe formula I to liquid-crystalline base materials from other classes ofcompound in order, for example, to modify the dielectric and/or opticalanisotropy of a dielectric of this type and/or to optimise its thresholdvoltage and/or its viscosity. Addition of compounds of the formula I toliquid-crystalline dielectrics enables Δn values of such media to besignificantly reduced.

[0022] The meaning of the formula I includes all isotopes of thechemical elements bound in the compounds of the formula I. Inenantiomerically pure or enriched form, the compounds of the formula Iare also suitable as chiral dopants and in general for achieving chiralmesophases.

[0023] In the pure state, the compounds of the formula I are colorlessand form liquid-crystalline mesophases in a temperature range which isfavorably located for electro-optical use. They are stable chemically,thermally and to light.

[0024] The invention thus relates to the compounds of the formula I andto the use of these compounds as components of liquid-crystalline media.The invention furthermore relates to liquid-crystalline media comprisingat least one compound of the formula I and to liquid-crystal displayelements, in particular electro-optical display elements, which containmedia of this type.

[0025] Above and below, n, m, R¹, R², R³, X¹, X², X³, X⁴, Z¹, Z², A¹,A², Q, Y¹ and Y² are as defined above, unless expressly statedotherwise. If the radical X¹ occurs more than once, it may adoptidentical or different meanings. The same applies to all other groupswhich occur more than once.

[0026] For reasons of simplicity, Cyc below denotes acyclohexane-1,4-diyl radical or a 1- or 4-silacyclohexane-1,4-diylradical, Dio denotes a 1,3-dioxane-2,5-diyl radical, Dit denotes a1,3-dithiane-2,5-diyl radical, and Boc denotes a bicyclo[2,2,2]octyleneradical, where Cyc may be unsubstituted or monosubstituted orpolysubstituted by F or CN.

[0027] W denotes the following structural unit:

[0028] in which X¹, X², X³, X⁴, Q, Y¹, Y² and Z² are as defined above,and p is 0, 1, 2 or 3.

[0029] Preferred meanings of the group W are represented by thesub-formulae W1 to W7:

[0030] in which Z² and R³ are as defined above.

[0031] Formula I covers the preferred compounds of the sub-formulae Ia1to Ia12, which, besides the group W, contain a six-membered ring:R¹-W-Cyc-R² Ia1 R¹-W-CH₂CH₂-Cyc-R² Ia2 R¹-W-COO-Cyc-R² Ia3 R¹-W-Dio-R²Ia4 R¹-W-CH₂CH₂-Dio-R² Ia5 R¹-W-COO-Dio-R² Ia6 R¹-Cyc-W-R² Ia7R¹-Dio-W-R² Ia8 R¹-Cyc-CH₂CH₂-W-R² Ia9 R¹-Dio-CH₂CH₂-W-R² Ia10R¹-Cyc-COO-W-R² Ia11 R¹-Dio-COO-W-R² Ia12

[0032] furthermore the likewise preferred compounds of the sub-formulaeIb1 to 1b72, which, in addition to the group W, contain two six-memberedrings: R¹-Cyc-Cyc-W-R² Ib1 R¹-Dio-Cyc-W-R² Ib2 R¹-Cyc-CH₂CH₂-Cyc-W-R²Ib3 R¹-Dio-CH₂CH₂-Cyc-W-R² Ib4 R¹-Cyc-COO-Cyc-W-R² Ib5R¹-Dio-COO-Cyc-W-R² Ib6 R¹-Cyc-Dio-W-R² Ib7 R¹-Dio-Dio-W-R² Ib8R¹-Cyc-CH₂CH₂-W-R² Ib9 R¹-Dio-CH₂CH₂-W-R² Ib10 R¹-Cyc-COO-Dio-W-R² Ib11R¹-Dio-COO-Dio-W-R² Ib12 R¹-Cyc-Cyc-CH₂CH₂-W-R² Ib13R¹-Dio-Cyc-CH₂CH₂-W-R² Ib14 R¹-Cyc-Dio-CH₂CH₂-W-R² Ib15R¹-Dio-Dio-CH₂CH₂-W-R² Ib16 R¹-Cyc-Cyc-COO-W-R² Ib17 R¹-Dio-Cyc-COO-W-R²Ib18 R¹-Cyc-Dio-COO-W-R² Ib19 R¹-Dio-Dio-COO-W-R² Ib20 R¹-Cyc-W-Cyc-R²Ib21 R¹-Dio-W-Cyc-R² Ib22 R¹-Cyc-CH₂CH₂-W-Cyc-R² Ib23R¹-Dio-CH₂CH₂-W-Cyc-R² Ib24 R¹-Cyc-COO-W-Cyc-R² Ib25 R¹-Dio-COO-W-Cyc-R²Ib26 R¹-Cyc-W-CH₂CH₂-Cyc-R² Ib27 R¹-Dio-W-CH₂CH₂-Cyc-R² Ib28R¹-Cyc-W-COO-Cyc-R² Ib29 R¹-Dio-W-COO-Cyc-R² Ib30 R¹-Cyc-W-Dio-R² Ib31R¹-Dio-W-Dio-R² Ib32 R¹-Cyc-CH₂CH₂-W-Dio-R² Ib33 R¹-Dio-CH₂CH₂-W-Dio-R²Ib34 R¹-Cyc-COO-W-Dio-R² Ib35 R¹-Dio-COO-W-Dio-R² Ib36R¹-Cyc-W-CH₂CH₂-Dio-R² Ib37 R¹-Dio-W-CH₂CH₂-Dio-R² Ib38R¹-Cyc-W-COO-Dio-R² Ib39 R¹-Dio-W-COO-Dio-R² Ib40 R¹-W-Cyc-Cyc-R² Ib41R¹-W-CH₂CH₂-Cyc-Cyc-R² Ib42 R¹-W-COO-Cyc-Cyc-R² Ib43 R¹-W-Dio-Cyc-R²Ib44 R¹-W-CH₂CH₂-Dio-Cyc-R² Ib45 R¹-W-COO-Dio-Cyc-R² Ib46R¹-W-Cyc-CH₂CH₂-Cyc-R² Ib47 R¹-W-Dio-CH₂CH₂-Cyc-R² Ib48R¹-W-Cyc-COO-Cyc-R² Ib49 R¹-W-Dio-COO-Cyc-R Ib50 R¹-W-Cyc-Dio-R² Ib51R¹-W-CH₂CH₂-Cyc-Dio-R² Ib52 R¹-W-COO-Cyc-Dio-R² Ib53 R¹-W-Dio-Dio-R²Ib54 R¹-W-CH₂CH₂-Dio-Dio-R² Ib55 R¹-W-COO-Dio-Dio-R² Ib56R¹-W-Cyc-CH₂CH₂-Dio-R² Ib57 R¹-W-Dio-CH₂CH₂-Dio-R² Ib58R¹-W-Cyc-COO-Dio-R² Ib59 R¹-W-Dio-COO-Dio-R² Ib60R¹-Cyc-CH₂CH₂-W-CH₂CH₂-Cyc-R² Ib61 R¹-Dio-CH₂CH₂-W-CH₂CH₂-Cyc-R² Ib62R¹-Cyc-CH₂CH₂-W-CH₂CH₂-Dio-R² Ib63 R¹-Dio-CH₂CH₂-W-CH₂CH₂-Dio-R² Ib64R¹-Cyc-CH₂CH₂-Cyc-CH₂CH₂-W-R² Ib65 R¹-Dio-CH₂CH₂-Cyc-CH₂CH₂-W-R² Ib66R¹-Cyc-CH₂CH₂-Dio-CH₂CH₂-W-R² Ib67 R¹-Dio-CH₂CH₂-Dio-CH₂CH₂-W-R² Ib68R¹-W-CH₂CH₂-Cyc-CH₂CH₂-Cyc-R² Ib69 R¹-W-CH₂CH₂-Dio-CH₂CH₂-Cyc-R² Ib70R¹-W-CH₂CH₂-Cyc-CH₂CH₂-Dio-R² Ib71 R¹-W-CH₂CH₂-Dio-CH₂CH₂-Dio-R² Ib72

[0033] and the preferred compounds of the sub-formulae 1c1 to 1c55,which, besides the group W, contain three six-membered rings:R¹-W-Cyc-Cyc-Cyc-R² Ic1 R¹-W-CH₂CH₂-Cyc-Cyc-Cyc-R² Ic2R¹-W-Dio-Cyc-Cyc-R² Ic3 R¹-W-CH₂CH₂-Dio-Cyc-Cyc-R² Ic4R¹-W-Cyc-CH₂CH₂-Cyc-Cyc-R² Ic5 R¹-W-Dio-CH₂CH₂-Cyc-Cyc-R² Ic6R¹-W-Cyc-Cyc-CH₂CH₂-Cyc-R² Ic7 R¹-W-Dio-Cyc-CH₂CH₂-Cyc-R² Ic8R¹-W-Cyc-Dio-Cyc-R² Ic9 R¹-W-CH₂CH₂-Cyc-Dio-Cyc-R² Ic10R¹-W-Dio-Dio-Cyc-R² Ic11 R¹-W-CH₂CH₂-Dio-Dio-Cyc-R² Ic12R¹-W-Cyc-CH₂CH₂-Dio-Cyc-R² Ic13 R¹-W-Dio-CH₂CH₂-Dio-Cyc-R² Ic14R¹-W-Cyc-Dio-CH₂CH₂-Cyc-R² Ic15 R¹-Cyc-Dio-CH₂CH₂-Cyc-W-R² Ic16R¹-Dio-Dio-CH₂CH₂-Cyc-W-R² Ic17 R¹-Cyc-Cyc-Cyc-CH₂CH₂-W-R² Ic18R¹-Dio-Cyc-Cyc-CH₂CH₂-W-R² Ic19 R¹-Cyc-Dio-Cyc-CH₂CH₂-W-R² Ic20R¹-Dio-Dio-Cyc-CH₂CH₂-W-R² Ic21 R¹-Cyc-Cyc-Dio-W-R² Ic22R¹-Dio-Cyc-Dio-W-R² Ic23 R¹-Cyc-CH₂CH₂-Cyc-Dio-W-R² Ic24R¹-Dio-CH₂CH₂-Cyc-Dio-W-R² Ic25 R¹-Cyc-Dio-Dio-W-R² Ic26R¹-Dio-Dio-Dio-W-R² Ic27 R¹-Cyc-CH₂CH₂-Dio-Dio-W-R² Ic28R¹-Dio-CH₂CH₂-Dio-Dio-W-R² Ic29 R¹-Cyc-Cyc-CH₂CH₂-Dio-W-R² Ic30R¹-Dio-Cyc-CH₂CH₂-Dio-W-R² Ic31 R¹-Cyc-CH₂CH₂-Dio-W-Dio-R² Ic32R¹-Dio-CH₂CH₂-Dio-W-Dio-R² Ic33 R¹-Cyc-Cyc-CH₂CH₂-W-Dio-R² Ic34R¹-Dio-Cyc-CH₂CH₂-W-Dio-R² Ic35 R¹-Cyc-Dio-CH₂CH₂-W-Dio-R² Ic36R¹-Dio-Dio-CH₂CH₂-W-Dio-R² Ic37 R¹-Cyc-Cyc-W-CH₂CH₂-Dio-R² Ic38R¹-Dio-Cyc-W-CH₂CH₂-Dio-R² Ic39 R¹-Cyc-Dio-W-CH₂CH₂-Dio-R² Ic40R¹-Dio-Dio-W-CH₂CH₂-Dio-R² Ic41 R¹-Cyc-W-Dio-CH₂CH₂-Cyc-R² Ic42R¹-Dio-W-Dio-CH₂CH₂-Cyc-R² Ic43 R¹-Cyc-W-Cyc-Dio-R² Ic44R¹-Dio-W-Cyc-Dio-R² Ic45 R¹-Cyc-CH₂CH₂-W-Cyc-Dio-R² Ic46R¹-Dio-CH₂CH₂-W-Cyc-Dio-R² Ic47 R¹-Cyc-W-CH₂CH₂-Cyc-Dio-R² Ic48R¹-Dio-W-CH₂CH₂-Cyc-Dio-R² Ic49 R¹-Cyc-W-Cyc-CH₂CH₂-Dio-R² Ic50R¹-Dio-W-Cyc-CH₂CH₂-Dio-R² Ic51 R¹-Cyc-W-Dio-Dio-R² Ic52R¹-Dio-W-Dio-Dio-R² Ic53 R¹-Cyc-CH₂CH₂-W-Dio-Dio-R² Ic54R¹-Dio-CH₂CH₂-W-Dio-Dio-R² Ic55

[0034] in which R¹, R², Cyc, Dio and W are as defined above.

[0035] Preference is given to compounds of the formula I which containno isolated or aromatic C, C double bonds.

[0036] R¹ and R² are preferably, independently of one another, F, OCF₃,CF₃, straight-chain alkyl or alkoxy having 1 to 15 carbon atoms, inparticular alkyl, alkenyl, alkenyloxy or alkoxy having up to 7 carbonatoms. In particular, preferably only one of the radicals R¹ and R² is astraight-chain alkenyl, alkoxy, alkenyl or alkenyloxy radical having upto 7 carbon atoms.

[0037] In preferred compounds of the formula I, X¹, X², X³ and/or X⁴ are—C≡C—C≡C—H, —C≡C—C≡C—alkyl, —C≡C—C≡C—Cl or —C≡C—C≡C—CN, where alkyl isan alkyl radical having to 1 to 15 carbon atoms. In particular, thealkyl radical is branched and is preferably tert-butyl.

[0038] In particularly preferred compounds of the formula I, X³ and X⁴are simultaneously H.

[0039] Preference is furthermore given to compounds of the formula I inwhich only one of the groups X¹, X², X³ and X⁴ is not H.

[0040] —C≡C—C≡C—R³ is preferably —C≡C—C≡C—C(alkyl*)₃,—C≡C—C≡C—C(alkyl*)(alkyl**)₂ or —C≡C—C≡C—CH(alkyl*)₂, in particular—C≡C—C≡C—C(CH₃)₃, —C≡C—C≡C—CH(CH₃)₂ or —C≡C—C≡C—C(CH₃)₂C₃H₇. alkyl* andalkyl** are each, independently of one another, CH₃, C₂H₅ or C₃H₇.

[0041] A¹ and/or A² are preferably Cyc or Dio.

[0042] Preference is also given to compounds of the formula I and of allsub-formulae in which A¹ and/or A² is cyclohexane-1,4-diyl which ismono-substituted or disubstituted by F or CN.

[0043] A¹ and/or A² is preferably

[0044] m and n are preferably 0, 1 or 2, in particular 0 or 1. m+n ispreferably 1 or 2.

[0045] Z¹ and Z² are preferably, independently of one another, —CH₂CH₂—,—CF₂O—, —OCF₂—, —COO—, —OOC— or a single bond, particularly preferably asingle bond or —CH₂—CH₂—.

[0046] Preference is given to compounds of the formula I in which R¹ andR² are simultaneously alkyl or alkoxy having 1 to 10 carbon atoms.

[0047] Preference is furthermore given to compounds of the formula I inwhich Y¹ and Y² are a carbon atom. Compounds of the formula I whichcontain not more than one dioxane ring likewise represent a preferredembodiment of the invention.

[0048] Particular preference is furthermore given to the compounds ofthe formulae I1 to I21 from the following group:

[0049] in which R¹, R², R³, Z¹, and Z² are as defined above.

[0050] If R¹ and/or R² in the formulae above and below are an alkylradical, this may be straight-chain or branched. It is preferablystraight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly ispreferably ethyl, propyl, butyl, pentyl, hexyl or heptyl, furthermoremethyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl orpentadecyl.

[0051] If R¹ and/or R² is an alkyl radical in which one CH₂ group hasbeen replaced by —O—, this may be straight-chain or branched. It ispreferably straight-chain and has 1 to 10 carbon atoms. The first CH₂group in this alkyl radical has preferably been replaced by —O—, so thatthe radical R¹ attains the meaning alkoxy and is preferably methoxy,ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy ornonyloxy.

[0052] It is furthermore also possible for a CH₂ group elsewhere to havebeen replaced by —O—, so that the radical R¹ and/or R² is preferablystraight-chain 2-oxapropyl (=methoxymethyl), 2- (=ethoxymethyl) or3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-oxadecyl.

[0053] If R¹ and/or R² is an alkenyl radical, this may be straight-chainor branched. It is preferably straight-chain and has 2 to 10 carbonatoms. Accordingly, it is in particular vinyl, prop-1- or -2-enyl,but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-,-4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-,-3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or-8-enyl, or dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

[0054] R¹ and/or R² is particularly preferably an alkenyl radical fromthe following group:

[0055] If R¹ and/or R² is an alkenyloxy radical, this may bestraight-chain or branched. It is preferably straight-chain and has 2 to10 carbon atoms. It is particularly preferably a radical from thefollowing group:

[0056] If R¹ and/or R² is an alkyl radical in which one CH₂ group hasbeen replaced by —O— and one has been replaced by —CO—, these arepreferably adjacent. These thus contain an acyloxy group —CO—O— or anoxycarbonyl group —O—CO—. These are preferably straight-chain and have 2to 6 carbon atoms.

[0057] Accordingly, they are in particular acetoxy, propionyloxy,butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl,propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl,2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetoxypropyl,3-propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl,ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl,3-(ethoxycarbonyl)propyl or 4-(methoxycarbonyl)butyl.

[0058] If R¹ and/or R² is an alkyl radical which is at leastmonosubstituted by halogen, this radical is preferably straight-chain.Halogen is preferably F or Cl. In the case of polysubstitution, halogenis preferably F. The resultant radicals also include perfluorinatedradicals. In the case of monosubstitution, the fluorine or chlorinesubstituent may be in any desired position, but is preferably in theω-position.

[0059] Compounds of the formula I having a branched wing group R¹ and/orR² may occasionally be of importance owing to better solubility in theconventional liquid-crystalline base materials, but in particular aschiral dopants if they are optically active. Smectic compounds of thistype are suitable as components of ferroelectric materials.

[0060] Branched groups of this type generally contain not more than onechain branch. Preferred branched radicals R¹ and/or R² are isopropyl,2-butyl (=1-methylpropyl), isobutyl (=2-methylpropyl), 2-methylbutyl,isopentyl (=3-methylbutyl), 2-methylpentyl, 3-methylpentyl,2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy,2-methylbutoxy, 3-methylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy,2-ethylhexyloxy, 1-methylhexyloxy or 1-methylheptyloxy.

[0061] Formula I covers both the racemates of these compounds and theoptical antipodes, and mixtures thereof.

[0062] Of these compounds of the formula I and the sub-formulae,preference is given to those in which at least one of the radicalspresent therein has one of the preferred meanings indicated.

[0063] Some very particularly preferred smaller groups of compounds ofthe formula I are those of the sub-formulae I22 to I36:

[0064] The compounds of the formula I are prepared by methods known perse, as described in the literature (for example in the standard works,such as Houben-Weyl, Methoden der Organischen Chemie [Methods of OrganicChemistry], Georg-Thieme-Verlag, Stuttgart), to be precise underreaction conditions which are known and suitable for the said reactions.

[0065] Use can be made here of variants which are known per se, but arenot mentioned in greater detail here.

[0066] If desired, the starting materials can also be formed in situ bynot isolating them from the reaction mixture, but instead immediatelyconverting them further into the compounds of the formula I.

[0067] The synthesis of the compounds of the formula I in which A¹and/or A² is axially fluorinated cyclohexane can be effected by usinghydrogen fluoride under pressure or by means of amine/hydrogen fluorideadducts (for example A. V. Grosse, C. B. Linn, J. Org. Chem. 3, (1938)26; G. A. Olah, M. Nojima, I. Kerekes, Synthesis, (1973) 779); G. A.Olah, X-Y. Li, Q. Wang, G. K. S. Prakash, Synthesis (1993) 693).

[0068] The compounds according to the invention can be prepared, forexample, in accordance with the following reaction schemes:

[0069] Esters of the formula I can also be obtained by esterification ofcorresponding carboxylic acids (or reactive derivatives thereof) usingalcohols or phenols (or reactive derivatives thereof) or by the DCCmethod (DCC=dicyclohexylcarbodiimide).

[0070] The corresponding carboxylic acids and alcohols are known or canbe prepared analogously to known processes.

[0071] Suitable reactive derivatives of the said carboxylic acids are inparticular the acid halides, especially the chlorides and bromides,furthermore the anhydrides, azides or esters, in particular alkyl estershaving 1-4 carbon atoms in the alkyl group.

[0072] Suitable reactive derivatives of the said alcohols are, inparticular, the corresponding metal alkoxides, preferably of an alkalimetal, such as Na or K.

[0073] The esterification is advantageously carried out in the presenceof an inert solvent. Highly suitable solvents are, in particular,ethers, such as diethyl ether, di-n-butyl ether, THF, dioxane andanisole, ketones, such as acetone, butanone or cyclohexanone, amides,such as DMF or hexamethylphosphoric triamide, hydrocarbons, such asbenzene, toluene or xylene, halogenated hydrocarbons, such astetrachloromethane or tetrachloroethylene, and sulfoxides, such asdimethyl sulfoxide or sulfolane. Water-immiscible solvents mayadvantageously be used at the same time for azeotropic removal bydistillation of the water formed during the esterification. An excess ofan organic base, for example pyridine, quinoline or triethylamine, mayoccasionally also be used as solvent for the esterification. Theesterification may also be carried out in the absence of a solvent, forexample by simple heating of the components in the presence of sodiumacetate. The reaction temperature is usually between −50° C. and +250°C., preferably between −20° C. and +80° C. At these temperatures, theesterification reactions are generally complete after from 15 minutes to48 hours.

[0074] In detail, the reaction conditions for the esterification dependsubstantially on the nature of the starting materials used. Thus, a freecarboxylic acid is generally reacted with a free alcohol in the presenceof a strong acid, for example a mineral acid, such as hydrochloric acidor sulfuric acid. A preferred reaction procedure is the reaction of anacid anhydride or in particular an acid chloride with an alcohol,preferably in a basic medium, important bases being, in particular,alkali metal hydroxides, such as sodium hydroxide or potassiumhydroxide, alkali metal carbonates or hydrogencarbonates, such as sodiumcarbonate, sodium hydrogencarbonate, potassium carbonate or potassiumhydrogencarbonate, alkali metal acetates, such as sodium acetate orpotassium acetate, alkaline earth metal hydroxides, such as calciumhydroxide, or organic bases, such as triethylamine, pyridine, lutidine,collidine or quinoline. A further preferred embodiment of theesterification comprises firstly converting the alcohol into the sodiumalkoxide or potassium alkoxide, for example by treatment with ethanolicsodium hydroxide solution or potassium hydroxide solution, isolatingthis alkoxide, and reacting it with an acid anhydride or in particularan acid chloride.

[0075] Nitriles can be obtained by replacement of halogens using coppercyanide or alkali metal cyanide.

[0076] Ethers of the formula I are obtainable by etherification ofcorresponding hydroxyl compounds, the hydroxyl compound advantageouslyfirstly being converted into a corresponding metal derivative, forexample into the corresponding alkali metal alkoxide by treatment withNaH, NaNH₂, NaOH, KOH, Na₂CO₃ or K₂CO₃. This alkali metal alkoxide canthen be reacted with the corresponding alkyl halide, alkyl sulfonate ordialkyl sulfate, advantageously in an inert solvent, such as, forexample,. acetone, 1,2-dimethoxyethane, DMF or dimethyl sulfoxide, oralso with an excess of aqueous or aqueous-alcoholic NaOH or KOH, attemperatures between about 20° C. and 100° C.

[0077] The organometallic compounds are prepared, for example, bymetal-halogen exchange (for example in accordance with Org. React. 6,339-366 (1951)) between the corresponding halogen compound and anorganolithium compound, such as, preferably, tert-butyllithium orlithium naphthalenide, or by reaction with magnesium turnings.

[0078] In addition, the compounds of the formula I can be prepared byreducing a compound which conforms to the formula I, but contains one ormore reducible groups and/or C—C bonds in place of H atoms.

[0079] Suitable reducible groups are preferably carbonyl groups, inparticular keto groups, furthermore, for example, free or esterifiedhydroxyl groups or aromatically bound halogen atoms. Preferred startingmaterials for the reduction are compounds conforming to the formula I,but which contain a cyclohexene ring or cyclohexanone ring instead of acyclohexane ring and/or contain a —CH₂CH₂— group instead of a —CH═CH—group and/or contain a —CO— group instead of a —CH₂— group and/orcontain a free or functionally (for example in the form of itsp-toluenesulfonate) modified OH group instead of an H atom.

[0080] The reduction can be carried out, for example, by catalytichydrogenation at temperatures between about 0° C. and about 200° C. andpressures between about 1 and 200 bar in an inert solvent, for examplean alcohol, such as methanol, ethanol or isopropanol, an ether, such astetrahydrofuran (THF) or dioxane, an ester, such as ethyl acetate, acarboxylic acid, such as acetic acid, or a hydrocarbon, such ascyclohexane. Suitable catalysts are advantageously noble metals, such asPt or Pd, which can be employed in the form of oxides (for example PtO₂or PdO), on a support (for example Pd on carbon, calcium carbonate orstrontium carbonate) or in finely divided form.

[0081] Ketones can also be reduced to the corresponding compounds of theformula I containing alkyl groups and/or —CH₂CH₂— bridges by the methodsof Clemmensen (using zinc, zinc amalgam or tin and hydrochloric acid,advantageously in aqueous-alcoholic solution or in the heterogeneousphase with water/toluene at temperatures between about 80 and 120° C.)or Wolff-Kishner (using hydrazine, advantageously in the presence ofalkali, such as KOH or NaOH, in a high-boiling solvent, such asdiethylene glycol or triethylene glycol, at temperatures between about100 and 200° C.).

[0082] Furthermore, reductions with complex hydrides are possible. Forexample, arylsulfonyloxy groups can be removed reductively using LiAlH₄,in particular p-toluenesulfonyloxymethyl groups can be reduced to methylgroups, advantageously in an inert solvent, such as diethyl ether orTHF, at temperatures between about 0 and 100° C.

[0083] Double bonds can be hydrogenated using NaBH₄ or tributyltinhydride in methanol.

[0084] The starting materials are either known or can be preparedanalogously to known compounds.

[0085] The liquid-crystalline media according to the inventionpreferably comprise from 2 to 40, in particular from 4 to 30, componentsas further constituents besides one or more compounds according to theinvention. These media very particularly preferably comprise from 7 to25 components besides one or more compounds according to the invention.These further constituents are preferably selected from nematic ornematogenic (monotropic or isotropic) substances, in particularsubstances from the classes of the azoxybenzenes, benzylideneanilines,biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl orcyclohexyl esters of cyclohexanecarboxylic acid, phenyl or cyclohexylesters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters ofcyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoicacid, of cyclohexanecarboxylic acid or ofcyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes,cyclohexylbiphenyls, phenylcyclohexylcyclohexanes,cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes,1,4-biscyclohexylbenzenes, 4,4′-biscyclohexylbiphenyls, phenyl- orcyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- orcyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes,1,2-diphenylethanes, 1,2-dicyclohexylethanes,1-phenyl-2-cyclohexylethanes,1-cyclohexyl-2-(4-phenylcyclohexyl)ethanes,1-cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexylphenylethanes,optionally halogenated stilbenes, benzyl phenyl ethers, tolans,naphthalenes, decalins and substituted cinnamic acids. The 1,4-phenylenegroups in these compounds may also be fluorinated.

[0086] The most important compounds suitable as further constituents ofmedia according to the invention can be characterised by the formulae 1,2, 3, 4 and 5: R′-L-E-R″ 1 R′-L-COO-E-R″ 2 R′-L-OOC-E-R″ 3R′-L-CH₂CH₂-E-R″ 4 R′-L-C≡C-E-R″ 5

[0087] In the formulae 1, 2, 3, 4 and 5, L and E, which may be identicalor different, are each, independently of one another, a divalent radicalfrom the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-,-Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images, where Phe isunsubstituted or fluorine-substituted 1,4-phenylene, Cyc istrans-1,4-cyclohexylene or 1,4-cyclohexylene, Pyr is pyrimidine-2,5-diylor pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyl, and G is2-(trans-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or1,3-dioxane-2,5-diyl.

[0088] One of the radicals L and E is preferably Cyc, Phe or Pyr. E ispreferably Cyc, Phe or Phe-Cyc. The media according to the inventionpreferably comprise one or more components selected from the compoundsof the formulae 1, 2, 3, 4 and 5 in which L and E are selected from thegroup consisting of Cyc, Phe and Pyr and simultaneously one or morecomponents selected from the compounds of the formulae 1, 2, 3, 4 and 5in which one of the radicals L and E is selected from the groupconsisting of Cyc, Phe and Pyr and the other radical is selected fromthe group consisting of -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and-G-Cyc-, and optionally one or more components selected from thecompounds of the formulae 1, 2, 3, 4 and 5 in which the radicals L and Eare selected from the group consisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe-and -G-Cyc-.

[0089] In a smaller sub-group of the compounds of the formulae 1, 2, 3,4 and 5, R′ and R″ are each, independently of one another, alkyl,alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8carbon atoms. This smaller sub-group is called group A below, and thecompounds are referred to by the sub-formulae 1a, 2a, 3a, 4a and 5a. Inmost of these compounds, R′ and R″ are different from one another, oneof these radicals usually being alkyl, alkenyl, alkoxy, alkenyloxy oralkoxyalkyl.

[0090] In another smaller sub-group of the compounds of the formulae 1,2, 3, 4 and 5, which is known as group B, R″ is —F, —Cl, —NCS or—(O)_(i)CH_(3-(k+I))F_(k)Cl_(I), where i is 0 or 1, and k and I are 1, 2or 3; the compounds in which R″ has this meaning are referred to by thesub-formulae 1b, 2b, 3b, 4b and 5b. Particular preference is given tothose compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b in which R″ is—F, —Cl, —NCS, —CF₃, —OCHF₂ or —OCF₃.

[0091] In the compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b, R′ isas defined for the compounds of the sub-formulae 1a-5a and is preferablyalkyl, alkenyl, alkoxy, alkenyloxy or alkoxyalkyl.

[0092] In a further smaller sub-group of the compounds of the formulae1, 2, 3, 4 and 5, R″ is —CN; this sub-group is referred to below asgroup C, and the compounds of this sub-group are correspondinglydescribed by sub-formulae 1c, 2c, 3c, 4c and 5c. In the compounds of thesub-formulae 1c, 2c, 3c, 4c and 5c, R′ is as defined for the compoundsof the sub-formulae 1a-5a and is preferably alkyl, alkoxy or alkenyl.

[0093] Besides the preferred compounds of groups A, B and C, othercompounds of the formulae 1, 2, 3, 4 and 5 having other variants of theproposed substituents are also customary. All these substances areobtainable by methods which are known from the literature or analogouslythereto.

[0094] Besides the compounds of the formula I according to theinvention, the media according to the invention preferably comprise oneor more compounds selected from group A and/or group B and/or group C.The proportions by weight of the compounds from these groups in themedia according to the invention are preferably group A: from 0 to 90%,preferably from 20 to 90%, in particular from 30 to 90% group B: from 0to 80%, preferably from 10 to 80%, in particular from 10 to 65% group C:from 0 to 80%, preferably from 5 to 80%, in particular from 5 to 50%,

[0095] the sum of the proportions by weight of the group A and/or Band/or C compounds present in the respective media according to theinvention preferably being 5 to 90% and in particular from 10% to 90%.

[0096] The media according to the invention preferably comprise from 1to 40%, particularly preferably from 5 to 30%, of the compoundsaccording to the invention. Preference is furthermore given to mediacomprising more than 40%, in particular from 45 to 90%, of compoundsaccording to the invention. The media preferably comprise one or two,furthermore three to four compounds according to the invention.

[0097] The media according to the invention are prepared in a mannerwhich is conventional per se. In general, the components are dissolvedin one another, advantageously at elevated temperature. By means ofsuitable additives, the liquid-crystalline phases according to theinvention can be modified in such a way that they can be used in alltypes of liquid-crystal display elements that have been disclosedhitherto. Additives of this type are known to the person skilled in theart and are described in detail in the literature (H. Kelker/R. Hatz,Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). Forexample, pleochroic dyes can be added for the preparation of coloredguest-host systems or substances can be added to modify the dielectricanisotropy, the viscosity and/or alignment of the nematic phases.

[0098] The entire disclosure of all applications, patents andpublications, cited above and of corresponding German application No.10035651.6, filed Jul. 20, 2000 is hereby incorporated by reference.

EXAMPLES

[0099] The following examples are intended to illustrate the inventionwithout representing a limitation. Above and below, percentages arepercent by weight. All temperatures are given in degrees Celsius. m.p.denotes melting point, cl.p.=clearing point. Furthermore, C=crystallinestate, N=nematic phase, Sn=smectic phase and I=isotropic phase. The databetween these symbols represent the transition temperatures. An denotesoptical anisotropy (589 nm, 20° C.) and Δε denotes the dielectricanisotropy (1 kHz, 20° C.).

[0100] “Conventional work-up” means that water is added if necessary,the mixture is extracted with methylene chloride, diethyl ether ortoluene, the phases are separated, the organic phase is dried andevaporated, and the product is purified by distillation under reducedpressure or crystallization and/or chromatography.

[0101] The following abbreviations are used: THF tetrahydrofuran KOtBupotassium tert-butoxide MTB ether methyl tert-butyl ether DMSO dimethylsulfoxide

Example 1

[0102]

[0103] Step 1.1

[0104] 640 mmol of A are dissolved in 800 ml of toluene, and 755 mmol ofdiisobutylaluminium hydride are added dropwise to this mixture. Themixture is stirred at room temperature for about 2 hours. The reactionmixture is poured into ice/HCl, and the resultant two-phase mixture isstirred well for about 1 hour so that the resultant imine is hydrolyzedto the aldehyde. The reaction mixture is extracted with toluene, thecombined organic phases are washed with water, dried over sodium sulfateand filtered, and the product is subjected to conventional work-up.

[0105] Step 1.2

[0106] 651 mmol of (trimethylsilyl)acetylene are dissolved in 300 ml ofabs. THF, and 651 mmol of BuLi (15% solution in n-hexane) are addeddropwise at from 0 to −10° C. After the mixture has been stirred forabout 10 minutes, 542 mmol of B dissolved in 350 ml of abs. THF areadded dropwise at from 0 to −10° C. The mixture is stirred for a further1 hour, water is carefully added, and the mixture is subjected toconventional work-up.

[0107] Step 1.3

[0108] 1.3 mol of KOH dissolved in 1500 ml of methanol are added to 0.54mol of C. The reaction mixture is stirred at room temperature overnight,water is added, and the mixture is neutralised using HCl. Finally, themixture is subjected to conventional work-up.

[0109] Step 1.4

[0110] 89 mmol of D in 100 ml of abs. THF are initially introduced, and179 mmol of BuLi (15% solution in n-hexane) are added at from 0 to −10°C. The reaction mixture is stirred for 10 minutes, and 89 mmol ofpivalaldehyde dissolved in 40 ml of abs. THF are added at from 0 to −10°C. The reaction mixture is stirred for 1 hour, water is added, and themixture is acidified using dilute HCl and subjected to conventionalwork-up.

[0111] Step 1.5

[0112] 180 mmol of thionyl chloride are added at room temperature to 60mmol of E dissolved in 100 ml of dichloromethanol. After the reactionmixture has been stirred for 48 hours, water is added, and the mixtureis subjected to conventional work-up.

[0113] Step 1.6

[0114] 50 mmol of F are dissolved in 100 ml of abs. DMSO, 150 mmol ofKO^(t)Bu are added in portions, and the mixture is stirred at 120° C.for 2 hours. The reaction mixture is allowed to cool, and dilute HCl iscarefully added. Finally, the mixture is subjected to conventionalwork-up. The product is recrystallised from n-hexane/i-propanol (1:10).

C 84 N (23.6)I; Δn=−0.059; Δε=−3.8

[0115] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ (A¹—Z¹)_(n) X² X¹ R² n-Pentoxy

—C≡C—C≡C—CH(CH₃)₂ H n-Propyl n-Propyl

—C≡C—C≡C—CH₃ H OCF₃ n-Pentyl

—C≡C—C≡C—CH₃ H CF₃ Ethoxy

—C≡C—C≡C—CF₃ H F n-Pentyl

—C≡C—C≡C—C(CH₃)₃ H n-Pentyloxy n-Pentyl

—C≡C—C≡C—CH₃ H CF₃CF₃ H

—C≡C—C≡C—C(CH₃)₃ H n-Propyl Pentyloxy

—C≡C—C≡C—CF₃ H CHFCF₃ n-Pentyl

H —C≡C—C≡C—CF₃ n-Propyl n-Propyl

H —C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

H —C≡C—C≡C—CF₃ n-Propyl n-Propyl

H —C≡C—C≡C—C(CH₃)₃ n-Propyl Ethoxy

—C≡C—C≡C—CH₃ —C≡C—C≡C—CH₃ Methyl Hexyloxy

H —C≡C—C≡C—CF₃ n-Propoxy n-Pentyl

—C≡CH —C≡C—C≡C—C(CH₃)₃ n-Propoxy n-Propyl

H —C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

H —C≡C—C≡C—C(C₃H₇)(CH₃)₂ n-Propyl n-Pentyloxy

H —C≡C—C≡C—CF₃ Methyl n-Pentyl

H —C≡C—C≡C—C(CH₃)₃ n-Pentyl

[0116] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ (Z²—A²)_(n) X¹ X² R² n-Propyl

—C≡C—C≡C—C(CH₃)₃ H CHFCF₃ n-Pentyloxy

—C≡C—C≡C—Cl H n-Propyl n-Propyl

—C≡C—C≡C—CF₃ H OCF₃ n-Pentyl

—C≡C—C≡C—C(CH₃)₃ H CF₃ Ethoxy

—C≡C—C≡C—C(CH₃)₃ H F n-Hexyloxy

—C≡C—C≡C—Cl H n-Propoxy n-Pentyl

—C≡C—C≡C—CH₃ H CF₂CF₃ n-Propyl

—C≡C—C≡C—C(CH₃)₃ H n-Propyl n-Pentyloxy

—C≡C—C≡C—C(CH₃)₃ H CHFCF₃ n-Propyl

—C≡C—C≡C—Cl H OCF₃

[0117]

R¹ Z¹ Z² X¹ X² R² n-Pentyloxy — — —C≡C—C≡C—C(CH₃)₃ H CHFCF₃ n-Propyl — ——C≡C—C≡C—C(CH₃)₃ H n-Propyl n-Propyl —CH₂CH₂— — —C≡C—C≡C—CF₃ H n-Propyln-Pentyl — —COO— —C≡C—C≡C—CH₃ H CF₃ n-Propyl —CH₂CH₂— —CH₂CH₂——C≡C—C≡C—C(CH₃)₃ —C≡C—C≡C—Cl n-Propyl n-Hexyloxy —CH₂CH₂— ——C≡C—C≡C—C(CH₃)₃ H n-Propoxy n-Pentyl — — —C≡C—C≡C—Cl H CF₂CF₃ n-Propyl— — —C≡C—C≡C—C(CH₃)₃ —C≡C—C≡C—SF₅ n-Propyl n-Pentyloxy — ——C≡C—C≡C—C(CH₃)₃ H CHFCF₃ n-Propyl —OOC— — —C≡C—C≡C—CH₃ H OCF₃ n-Propyl—OOC— —CH₂CH₂— H —C≡C—C≡C—CF₃ CHFCF₃ n-Pentyloxy — — H —C≡C—C≡C—C(CH₃)₃n-Pentyl n-Propyl — —OOC— H —C≡C—C≡C—CH₃ n-Propyl n-Pentyl —CH₂CH₂— — H—C≡C—C≡C—C(CH₃)₃ n-Propyl Ethoxy — — H —C≡C—C≡C—CH₃ Methyl n-Hexyloxy ——CH₂CH₂— H —C≡C—C≡C—C(CH₃)₃ n-Propoxy n-Pentyl — — H —C≡C—C≡C—Cln-Propoxy n-Propyl CF₂O— — H —C≡C—C≡C—H n-Propyl n-Propyl — —CF₂O— H—C≡C—C≡C—H n-Propyl n-Pentyl —CF₂O— — H —C≡C—C≡C—H n-Pentyl n-Pentyl ——CF₂O— H —C≡C—C≡C—H n-Pentyl n-Propyl — —CH₂CH₂— H —C≡C—C≡C—C(CH₃)₃n-Propyl n-Pentyloxy —OOC— — H —C≡C—C≡C—C(CH₃)₃ Methyl n-Pentyl — — H—C≡C—C≡C—CH₃ n-Pentyl

[0118] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ Z¹ Z² X¹ X² R² n-Pentyloxy — — —C≡C—C≡C—C(CH₃)₃ H CHFCF₃ n-Pentoxy —— —C≡C—C≡C—Cl n-Propyl n-Propyl — —CH₂CH₂— —C≡C—C≡C—Cl —C≡C—C≡C—Cl OCF₃n-Pentyl — —COO— —C≡C—C≡C—CH H CF₃ Ethoxy —CH₂CH₂— —CH₂CH₂——C≡C—C≡C—C(CH₃)₃ H F n-Hexyloxy —CH₂CH₂— — —C≡C—C≡C—Cl H n-Propoxyn-Pentyl — — —C≡C—C≡C—CF₃ —C≡C—C≡C—CF₃ CF₂CF₃ n-Propyl — ——C≡C—C≡C—C(CH₃)₃ H n-Propyl n-Pentyloxy — — —C≡C—C≡C—C(CH₃)₃ H CHFCF₃n-Propyl — —OOC— —C≡C—C≡C—C(CH₃)₃ H OCF₃ n-Propyl —OOC— —CH₂CH₂— H—C≡C—C≡C—CH₃ CHFCF₃ n-Pentyloxy — — —C≡C—C≡C—C(CH₃)₃ —C≡C—C≡C—C(CH₃)₃n-Pentyl n-Propyl — — H —C≡C—C≡C—C(CH₃)₃ n-Propyl n-Pentyl —CH₂CH₂— — H—C≡C—C≡C—Cl n-Propyl n-Propyl —CF₂O— — H —C≡C—C≡C—H n-Propyl n-Propyl ——CF₂O— H —C≡C—C≡C—H n-Propyl n-Propyl —CF₂O— — H —C≡C—C≡C—H n-Pentyln-Propyl — —CF₂O— H —C≡C—C≡C—H n-Pentyl Ethoxy — — —C≡C—C≡C—C(CH₃)₃—C≡C—C≡C—C(CH₃)₃ Methyl n-Hexyloxy — —CH₂CH₂— H —C≡C—C≡C—Cl n-Propoxyn-Pentyl — — H —C≡C—C≡C—C(CH₃)₃ n-Propoxy n-Propyl —CH₂CH₂— — H—C≡C—C≡C—C(CH₃)₃ n-Propyl n-Pentyloxy —OOC— — H —C≡C—C≡C—C(CH₃)₃ Methyln-Pentyl — — H —C≡C—C≡C—Cl n-Pentyl

[0119] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ (A¹—Z¹)_(n) X⁵ R⁵ n-Propyl

—C≡C—C≡C—C(CH₃)₃

n-Pentyloxy

—C≡C—C≡C—CH₃ n-Propoxy n-Propoxy — —C≡C—C≡C—CF₃ OCF₃ n-Pentyl

—C≡C—C≡C—C(CH₃)₃ OCH₃ Ethyl

—C≡C—C≡C—C(CH₃)₃ n-Propoxy n-Hexyl

—C≡C—C≡C—C(CH₃)₃

n-Pentyloxy — —C≡C—C≡C—Cl OCF₂CF₃ n-Propyl

—C≡C—C≡C—C(CH₃)₃ n-Pentyloxy n-Butyl

—C≡C—C≡C—C(CH₃)₃ OCF═CF₂ n-Propoxy — —C≡C—C≡C—C(CH₃)₃ OCF₃ n-Propyl

—C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

—C≡C—C≡C—C(CH₃)₃ F n-Propyl

—C≡C—C≡C—C(CH₃)₃ OCF₃ n-Propyl

—C≡C—C≡C—C(C₂H₅)₂C₃H₇ CF₃

[0120] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ (A¹—Z¹)_(n) X² R² n-Propyl

—C≡C—C≡C—C(CH₃)₃ CHFCF₃ n-Pentyloxy

—C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

—C≡C—C≡C—CH₃ OCF₃ Ethoxy

—C≡C—C≡C—C(CH₃)₃ F n-Hexyloxy

—C≡C—C≡C—C(CH₃)₃ n-Propoxy n-Propyl

—C≡C—C≡C—CF₃ n-Propyl n-Pentyloxy

—C≡C—C≡C—C(CH₃)₃ CHFCF₃ n-Propyl

—C≡C—C≡C—CH₃ OCF₃ n-Propyl

—C≡C—C≡C—CH₃ CF₃ n-Propyl

—C≡C—C≡C—CH₃ F

[0121] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ (A¹—Z¹)_(n) X¹ X² R² n-Propyl

—C≡C—C≡C—C(CH₃)₃ H CHFCF₃ n-Pentyloxy

—C≡C—C≡C—C(CH₃)₃ —C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

—C≡C—C≡C—C(CH₃)₃ H OCF₃ Ethoxy

—C≡C—C≡C—Cl H F n-Propyl

—C≡C—C≡C—H H n-Propyl n-Propyl

—C≡C—C≡C—H H F n-Propyl

—C≡C—C≡C—H H CF₃ n-Pentyl

—C≡C—C≡C—H H n-Propyl n-Pentyl

—C≡C—C≡C—H H F n-Pentyl

—C≡C—C≡C—H H CF₃ n-Hexyloxy

—C≡C—C≡C—C(CH₃)₃ —C≡C—C≡C—CN n-Propoxy n-Pentyl

—C≡C—C≡C—CH₃ H n-Propyl n-Propoxy

—C≡C—C≡C—Cl H CHFCF₃

[0122]

R¹ (A¹—Z¹)_(n) X² R² n-Propyl

—C≡C—C≡C—C(CH₃)₃ CHFCF₃ n-Pentyloxy

—C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

—C≡C—C≡C—Cl OCF₃ n-Hexyloxy

—C≡C—C≡C—CF₃ n-Propoxy n-Propyl

—C≡C—C≡C—C(CH₃)₃ n-Propyl n-Pentoxy

—C≡C—C≡C—C(CH₃)₃ CHFCF₃ n-Propyl

—C≡C—C≡C—CH₃ OCF₃ n-Propyl

—C≡C—C≡C—CH₃ n-Propyl n-Propyl

—C≡C—C≡C—CH₃ F n-Propyl

—C≡C—C≡C—CH₃ CF₃ Vinyl

—C≡C—C≡C—CH₃ n-Propyl Vinyl

—C≡C—C≡C—CH(C₂H₅)₂ n-Propyl

[0123] The following compounds according to the invention are preparedanalogously using the corresponding precursors:

R¹ (Z²—A²)_(m) X⁴ R² n-Pentyl- oxy

—C≡C—C≡C—C(CH₃)₃ n-Propyl n-Propyl

—C≡C—C≡C—CH₃ OCF₃ n-Pentyl

—C≡C—C≡C—C(CH₃)₃ CF₃ Ethyl

—C≡C—C≡C—CF₃ F n-Hexyl

—C≡C—C≡C—C(CH₃)₃ n-Propoxy n-Pentyl

—C≡C—C≡C—CH₃ CF₃CF₃ n-Pentyl

—C≡C—C≡C—CH₃ n-Pentyl- oxy n-Propoxy

—C≡C—C≡C—CF₃ CHFCF₃

[0124] The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

[0125] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A dialkyne compound of the formula I

in which R¹ and R², independently of one another, are H, F, or an alkylradical having 1-15 carbon atoms which is unsubstituted ormonosubstituted to perhalo substituted by halogen or substituted by CNand in which, one or more CH₂ groups are optionally, independently ofone another, replaced by —O—, —S—, —CO—,

—CO—O—, —O—CO—, —O—CO—O— or —CH═CH— in such a way that heteroatoms arenot connected directly, X¹, X², X³ and X⁴ are each, independently of oneanother, H or —C≡C—C≡C—R³, provided that at least one of the groups X¹,X², X³ and X⁴ is —C≡C—C≡C—R³, R³ is H, Cl, CN, SF₅, CF₃, or an alkylradical having 1-15 carbon atoms which is unsubstituted ormono-substituted to perhalo substituted by halogen and in which, one ormore CH₂ groups are optionally replaced, in each case independently ofone another, by —CH═CH— or —O— in such a way that —O— atoms are notconnected directly, Q is —CH₂— or —O—, Y¹ and Y², independently of oneanother, are C or Si, A¹ and A², independently of one another, are atrans-1,4-cyclohexylene radical which is unsubstituted or substituted byF or CN and in which, one or more non-adjacent CH₂ groups are optionallyreplaced by —O— and/or —S—, or are

Z¹ and Z² are each, independently of one another, —CO—O—, —O—CO—,—CH₂O—, —O—, —OCH₂—, —CF₂O—, —OCF₂—, —CF₂CF₂—, —CF═CF—, —CH₂CH₂—,—CH═CH— or a single bond, and n and m, independently of one another, are0, 1, 2 or 3, where m+n is 1, 2 or
 3. 2. A dialkyne compound accordingto claim 1, which exhibits an optical anisotropy value Δn of <0.03 at areduced temperature of 0.9 and a wavelength of 589 nm.
 3. A dialkynecompound according to claim 1, wherein Y¹ and Y² are C.
 4. A dialkynecompound according to claim 1, wherein m and n are 0, 1 or
 2. 5. Adialkyne compound according to claim 1, wherein Z¹ and Z², independentlyof one another, are —CH₂CH₂—, —COO—, —OOC—, —CF₂O—, —OCF₂— or a singlebond.
 6. A dialkyne compound according to claim 1, wherein R¹ and R² aresimultaneously straight-chain alkyl or alkoxy having 1 to 10 carbonatoms.
 7. A dialkyne compound according to claim 1, wherein X¹, X², X³and/or X⁴ are —C≡C—C≡C—CH(alkyl*)₂, —C≡C—C≡C—C(alkyl*)(alkyl**)₂ or—C≡C—C≡C—C(alkyl*)₃, where alkyl* and alkyl** are each, independently ofone another, CH₃, C₂H₅ or C₃H₇.
 8. A dialkyne compound according toclaim 1, wherein X³ and X⁴ are simultaneously H.
 9. A liquid-crystallinemedium having at least two liquid-crystalline components, whichcomprises at least one compound of the formula I of claim
 1. 10. Aliquid-crystal display element, which comprises a liquid-crystallinemedium according to claim
 9. 11. A reflective or transfectiveliquid-crystal display element, which comprises as dielectric, aliquid-crystalline medium according to claim
 9. 12. An electro-opticaldisplay element, which comprises, as dielectric, a liquid-crystallinemedium according to claim 9.